Rice kernel blight

Pathogen and disease type. The fungus Alternaria padwickii is the causal agent of kernel blight or stackburn disease in rice. It is a seed-borne pathogen that belongs to the fungal group responsible for significant discoloration and tissue necrosis in various parts of the rice plant.

Host range and distribution. The primary host of Alternaria padwickii is rice (Oryza sativa). While most prevalent in humid tropical and subtropical regions where rice cultivation is intensive, the pathogen is found globally wherever environmental conditions favor its development and persistence.

Symptoms of infection. Symptoms appear as distinctive dark or black spots on the rice grains, often causing shriveling and reduced germination rates. On leaves and sheaths, the fungus causes brown spots with irregular borders, which may eventually lead to the destruction of the leaf tissue and reduced photosynthesis.

Environmental conditions. The development of the disease is highly dependent on humidity and temperature. Warm, humid conditions (temperatures between 25°C and 30°C and humidity exceeding 85%) significantly accelerate the production of conidia and the infection of healthy plant tissues, especially during the grain filling stage.

Economic impact and control. The disease reduces the overall yield and the market value of the grain due to poor quality. Effective management requires an integrated approach to break the infection cycle:

• Strict selection of disease-free, high-quality seeds.
• Application of chemical fungicides as seed treatments before planting.
• Optimal irrigation management to avoid excessive humidity in the canopy.
• Implementation of proper crop rotation practices to reduce inoculum pressure in the soil.